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	$174.81	9.715%	$191.7928	$191.79	$191.80	$191.80
Purchase #2	$84.69	5.688%	$89.5072	$89.51	$89.50	$89.50
Purchase #3	$211.59	12.267%	$237.5457	$237.55	$237.55	$237.50
Purchase #4	$208.72	7.220%	$223.7896	$223.79	$223.80	$223.80
Purchase #5	$53.46	12.189%	$59.9762	$59.98	$60.00	$60.00
Purchase #6	$220.50	9.419%	$241.2689	$241.27	$241.25	$241.30
Purchase #7	$59.82	7.402%	$64.2479	$64.25	$64.25	$64.20
7 purchase totals =	$1,013.59		$1,108.1283	$1,108.14	$1,108.15	$1,108.10