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	$99.26	13.291%	$112.4526	$112.45	$112.45	$112.50
Purchase #2	$155.33	7.711%	$167.3075	$167.31	$167.30	$167.30
Purchase #3	$70.99	11.387%	$79.0736	$79.07	$79.05	$79.10
Purchase #4	$80.27	11.312%	$89.3501	$89.35	$89.35	$89.40
Purchase #5	$169.48	9.107%	$184.9145	$184.91	$184.90	$184.90
Purchase #6	$157.91	7.248%	$169.3553	$169.36	$169.35	$169.40
Purchase #7	$185.55	7.666%	$199.7743	$199.77	$199.75	$199.80
7 purchase totals =	$918.79		$1,002.2279	$1,002.22	$1,002.15	$1,002.40