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	$165.42	3.760%	$171.6398	$171.64	$171.65	$171.60
Purchase #2	$103.26	4.728%	$108.1421	$108.14	$108.15	$108.10
Purchase #3	$156.41	3.426%	$161.7686	$161.77	$161.75	$161.80
Purchase #4	$75.63	12.665%	$85.2085	$85.21	$85.20	$85.20
Purchase #5	$174.41	12.416%	$196.0647	$196.06	$196.05	$196.10
Purchase #6	$158.57	5.268%	$166.9235	$166.92	$166.90	$166.90
Purchase #7	$114.96	13.203%	$130.1382	$130.14	$130.15	$130.10
7 purchase totals =	$948.66		$1,019.8854	$1,019.88	$1,019.85	$1,019.80