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	$95.54	4.613%	$99.9473	$99.95	$99.95	$99.90
Purchase #2	$9.96	8.400%	$10.7966	$10.80	$10.80	$10.80
Purchase #3	$7.90	4.124%	$8.2258	$8.23	$8.25	$8.20
Purchase #4	$96.61	3.598%	$100.086	$100.09	$100.10	$100.10
Purchase #5	$148.89	3.321%	$153.8346	$153.83	$153.85	$153.80
Purchase #6	$141.98	12.157%	$159.2405	$159.24	$159.25	$159.20
Purchase #7	$189.33	3.609%	$196.1629	$196.16	$196.15	$196.20
7 purchase totals =	$690.21		$728.2937	$728.30	$728.35	$728.20