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	$188.58	3.673%	$195.5065	$195.51	$195.50	$195.50
Purchase #2	$159.62	5.721%	$168.7519	$168.75	$168.75	$168.80
Purchase #3	$203.61	5.133%	$214.0613	$214.06	$214.05	$214.10
Purchase #4	$59.31	5.364%	$62.4914	$62.49	$62.50	$62.50
Purchase #5	$225.60	7.408%	$242.3124	$242.31	$242.30	$242.30
Purchase #6	$58.74	5.280%	$61.8415	$61.84	$61.85	$61.80
Purchase #7	$80.50	7.637%	$86.6478	$86.65	$86.65	$86.60
7 purchase totals =	$975.96		$1,031.6128	$1,031.61	$1,031.60	$1,031.60