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	$167.78	10.206%	$184.9036	$184.90	$184.90	$184.90
Purchase #2	$172.79	10.786%	$191.4271	$191.43	$191.45	$191.40
Purchase #3	$70.91	8.165%	$76.6998	$76.70	$76.70	$76.70
Purchase #4	$77.74	10.820%	$86.1515	$86.15	$86.15	$86.20
Purchase #5	$30.45	12.773%	$34.3394	$34.34	$34.35	$34.30
Purchase #6	$112.51	9.517%	$123.2176	$123.22	$123.20	$123.20
Purchase #7	$82.30	8.834%	$89.5704	$89.57	$89.55	$89.60
7 purchase totals =	$714.48		$786.3094	$786.31	$786.30	$786.30