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	$220.81	10.260%	$243.4651	$243.47	$243.45	$243.50
Purchase #2	$118.33	7.450%	$127.1456	$127.15	$127.15	$127.10
Purchase #3	$90.31	11.372%	$100.5801	$100.58	$100.60	$100.60
Purchase #4	$163.62	6.558%	$174.3502	$174.35	$174.35	$174.40
Purchase #5	$78.60	7.109%	$84.1877	$84.19	$84.20	$84.20
Purchase #6	$127.73	10.226%	$140.7917	$140.79	$140.80	$140.80
Purchase #7	$53.99	6.110%	$57.2888	$57.29	$57.30	$57.30
7 purchase totals =	$853.39		$927.8092	$927.82	$927.85	$927.90