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	$168.40	3.438%	$174.1896	$174.19	$174.20	$174.20
Purchase #2	$155.73	8.273%	$168.6135	$168.61	$168.60	$168.60
Purchase #3	$71.50	12.200%	$80.223	$80.22	$80.20	$80.20
Purchase #4	$10.91	6.818%	$11.6538	$11.65	$11.65	$11.70
Purchase #5	$150.49	3.535%	$155.8098	$155.81	$155.80	$155.80
Purchase #6	$189.53	5.307%	$199.5884	$199.59	$199.60	$199.60
Purchase #7	$52.75	12.449%	$59.3168	$59.32	$59.30	$59.30
7 purchase totals =	$799.31		$849.3949	$849.39	$849.35	$849.40