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	$120.74	8.285%	$130.7433	$130.74	$130.75	$130.70
Purchase #2	$94.30	11.452%	$105.0992	$105.10	$105.10	$105.10
Purchase #3	$185.60	8.573%	$201.5115	$201.51	$201.50	$201.50
Purchase #4	$232.35	4.424%	$242.6292	$242.63	$242.65	$242.60
Purchase #5	$88.56	12.369%	$99.514	$99.51	$99.50	$99.50
Purchase #6	$136.72	8.416%	$148.2264	$148.23	$148.25	$148.20
Purchase #7	$77.33	6.173%	$82.1036	$82.10	$82.10	$82.10
7 purchase totals =	$935.60		$1,009.8272	$1,009.82	$1,009.85	$1,009.70