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	$196.41	6.479%	$209.1354	$209.14	$209.15	$209.10
Purchase #2	$106.76	9.263%	$116.6492	$116.65	$116.65	$116.60
Purchase #3	$72.74	6.296%	$77.3197	$77.32	$77.30	$77.30
Purchase #4	$95.73	7.592%	$102.9978	$103.00	$103.00	$103.00
Purchase #5	$47.53	9.659%	$52.1209	$52.12	$52.10	$52.10
Purchase #6	$193.80	3.539%	$200.6586	$200.66	$200.65	$200.70
Purchase #7	$194.25	13.102%	$219.7006	$219.70	$219.70	$219.70
7 purchase totals =	$907.22		$978.5822	$978.59	$978.55	$978.50