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	$159.96	7.626%	$172.1585	$172.16	$172.15	$172.20
Purchase #2	$223.66	4.275%	$233.2215	$233.22	$233.20	$233.20
Purchase #3	$57.41	7.104%	$61.4884	$61.49	$61.50	$61.50
Purchase #4	$102.73	12.554%	$115.6267	$115.63	$115.65	$115.60
Purchase #5	$57.49	6.377%	$61.1561	$61.16	$61.15	$61.20
Purchase #6	$107.99	10.124%	$118.9229	$118.92	$118.90	$118.90
Purchase #7	$223.62	8.796%	$243.2896	$243.29	$243.30	$243.30
7 purchase totals =	$932.86		$1,005.8637	$1,005.87	$1,005.85	$1,005.90