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	$169.47	3.180%	$174.8591	$174.86	$174.85	$174.90
Purchase #2	$80.94	8.799%	$88.0619	$88.06	$88.05	$88.10
Purchase #3	$30.58	9.550%	$33.5004	$33.50	$33.50	$33.50
Purchase #4	$79.86	7.527%	$85.8711	$85.87	$85.85	$85.90
Purchase #5	$110.37	9.308%	$120.6432	$120.64	$120.65	$120.60
Purchase #6	$47.96	13.571%	$54.4687	$54.47	$54.45	$54.50
Purchase #7	$36.43	5.168%	$38.3127	$38.31	$38.30	$38.30
7 purchase totals =	$555.61		$595.7171	$595.71	$595.65	$595.80