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	$167.54	8.470%	$181.7306	$181.73	$181.75	$181.70
Purchase #2	$96.25	4.258%	$100.3483	$100.35	$100.35	$100.30
Purchase #3	$125.31	12.709%	$141.2356	$141.24	$141.25	$141.20
Purchase #4	$210.39	12.113%	$235.8745	$235.87	$235.85	$235.90
Purchase #5	$93.28	6.278%	$99.1361	$99.14	$99.15	$99.10
Purchase #6	$104.77	6.115%	$111.1767	$111.18	$111.20	$111.20
Purchase #7	$234.33	7.427%	$251.7337	$251.73	$251.75	$251.70
7 purchase totals =	$1,031.87		$1,121.2355	$1,121.24	$1,121.30	$1,121.10