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	$175.69	6.241%	$186.6548	$186.65	$186.65	$186.70
Purchase #2	$83.75	7.653%	$90.1594	$90.16	$90.15	$90.20
Purchase #3	$160.46	12.419%	$180.3875	$180.39	$180.40	$180.40
Purchase #4	$237.43	8.116%	$256.6998	$256.70	$256.70	$256.70
Purchase #5	$104.47	9.662%	$114.5639	$114.56	$114.55	$114.60
Purchase #6	$53.98	6.654%	$57.5718	$57.57	$57.55	$57.60
Purchase #7	$102.38	8.744%	$111.3321	$111.33	$111.35	$111.30
7 purchase totals =	$918.16		$997.3693	$997.36	$997.35	$997.50