Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$159.49	6.498%	$169.8537	$169.85	$169.85	$169.90
Purchase #2	$142.33	6.467%	$151.5345	$151.53	$151.55	$151.50
Purchase #3	$167.87	13.221%	$190.0641	$190.06	$190.05	$190.10
Purchase #4	$245.64	7.596%	$264.2988	$264.30	$264.30	$264.30
Purchase #5	$122.41	4.274%	$127.6418	$127.64	$127.65	$127.60
Purchase #6	$249.92	10.780%	$276.8614	$276.86	$276.85	$276.90
Purchase #7	$194.26	3.152%	$200.3831	$200.38	$200.40	$200.40
7 purchase totals =	$1,281.92		$1,380.6374	$1,380.62	$1,380.65	$1,380.70