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	$99.49	12.839%	$112.2635	$112.26	$112.25	$112.30
Purchase #2	$174.70	12.336%	$196.251	$196.25	$196.25	$196.30
Purchase #3	$230.63	5.729%	$243.8428	$243.84	$243.85	$243.80
Purchase #4	$10.78	7.114%	$11.5469	$11.55	$11.55	$11.50
Purchase #5	$156.70	11.389%	$174.5466	$174.55	$174.55	$174.50
Purchase #6	$136.63	13.545%	$155.1365	$155.14	$155.15	$155.10
Purchase #7	$218.54	3.653%	$226.5233	$226.52	$226.50	$226.50
7 purchase totals =	$1,027.47		$1,120.1106	$1,120.11	$1,120.10	$1,120.00