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	$89.72	6.230%	$95.3096	$95.31	$95.30	$95.30
Purchase #2	$82.45	8.573%	$89.5184	$89.52	$89.50	$89.50
Purchase #3	$169.40	12.714%	$190.9375	$190.94	$190.95	$190.90
Purchase #4	$38.49	12.454%	$43.2835	$43.28	$43.30	$43.30
Purchase #5	$68.74	6.283%	$73.0589	$73.06	$73.05	$73.10
Purchase #6	$159.28	13.435%	$180.6793	$180.68	$180.70	$180.70
Purchase #7	$159.32	9.700%	$174.774	$174.77	$174.75	$174.80
7 purchase totals =	$767.40		$847.5612	$847.56	$847.55	$847.60