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	$139.60	11.272%	$155.3357	$155.34	$155.35	$155.30
Purchase #2	$37.99	6.153%	$40.3275	$40.33	$40.35	$40.30
Purchase #3	$92.95	3.448%	$96.1549	$96.15	$96.15	$96.20
Purchase #4	$92.40	5.530%	$97.5097	$97.51	$97.50	$97.50
Purchase #5	$127.93	11.119%	$142.1545	$142.15	$142.15	$142.20
Purchase #6	$218.25	5.429%	$230.0988	$230.10	$230.10	$230.10
Purchase #7	$215.48	11.175%	$239.5599	$239.56	$239.55	$239.60
7 purchase totals =	$924.60		$1,001.1410	$1,001.14	$1,001.15	$1,001.20