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	$137.81	8.160%	$149.0553	$149.06	$149.05	$149.10
Purchase #2	$54.73	12.623%	$61.6386	$61.64	$61.65	$61.60
Purchase #3	$161.74	12.242%	$181.5402	$181.54	$181.55	$181.50
Purchase #4	$245.45	7.728%	$264.4184	$264.42	$264.40	$264.40
Purchase #5	$238.92	13.728%	$271.7189	$271.72	$271.70	$271.70
Purchase #6	$41.51	3.128%	$42.8084	$42.81	$42.80	$42.80
Purchase #7	$137.76	7.858%	$148.5852	$148.59	$148.60	$148.60
7 purchase totals =	$1,017.92		$1,119.7650	$1,119.78	$1,119.75	$1,119.70