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	$118.34	6.591%	$126.1398	$126.14	$126.15	$126.10
Purchase #2	$95.61	4.709%	$100.1123	$100.11	$100.10	$100.10
Purchase #3	$6.85	6.700%	$7.309	$7.31	$7.30	$7.30
Purchase #4	$51.46	11.204%	$57.2256	$57.23	$57.25	$57.20
Purchase #5	$224.56	4.147%	$233.8725	$233.87	$233.85	$233.90
Purchase #6	$57.69	11.578%	$64.3693	$64.37	$64.35	$64.40
Purchase #7	$240.63	3.200%	$248.3302	$248.33	$248.35	$248.30
7 purchase totals =	$795.14		$837.3587	$837.36	$837.35	$837.30