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	$93.53	6.844%	$99.9312	$99.93	$99.95	$99.90
Purchase #2	$223.34	4.520%	$233.435	$233.44	$233.45	$233.40
Purchase #3	$70.89	4.171%	$73.8468	$73.85	$73.85	$73.80
Purchase #4	$130.31	3.709%	$135.1432	$135.14	$135.15	$135.10
Purchase #5	$225.91	6.799%	$241.2696	$241.27	$241.25	$241.30
Purchase #6	$214.73	8.570%	$233.1324	$233.13	$233.15	$233.10
Purchase #7	$177.82	5.874%	$188.2651	$188.27	$188.25	$188.30
7 purchase totals =	$1,136.53		$1,205.0233	$1,205.03	$1,205.05	$1,204.90