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	$157.63	9.543%	$172.6726	$172.67	$172.65	$172.70
Purchase #2	$119.89	11.423%	$133.585	$133.59	$133.60	$133.60
Purchase #3	$61.31	4.812%	$64.2602	$64.26	$64.25	$64.30
Purchase #4	$96.96	6.862%	$103.6134	$103.61	$103.60	$103.60
Purchase #5	$91.92	3.471%	$95.1105	$95.11	$95.10	$95.10
Purchase #6	$9.27	9.426%	$10.1438	$10.14	$10.15	$10.10
Purchase #7	$129.28	12.337%	$145.2293	$145.23	$145.25	$145.20
7 purchase totals =	$666.26		$724.6148	$724.61	$724.60	$724.60