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	$92.88	7.698%	$100.0299	$100.03	$100.05	$100.00
Purchase #2	$62.30	7.753%	$67.1301	$67.13	$67.15	$67.10
Purchase #3	$127.45	11.839%	$142.5388	$142.54	$142.55	$142.50
Purchase #4	$26.44	13.690%	$30.0596	$30.06	$30.05	$30.10
Purchase #5	$245.32	10.527%	$271.1448	$271.14	$271.15	$271.10
Purchase #6	$7.33	6.494%	$7.806	$7.81	$7.80	$7.80
Purchase #7	$172.82	4.180%	$180.0439	$180.04	$180.05	$180.00
7 purchase totals =	$734.54		$798.7531	$798.75	$798.80	$798.60