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	$226.95	4.820%	$237.889	$237.89	$237.90	$237.90
Purchase #2	$66.40	9.483%	$72.6967	$72.70	$72.70	$72.70
Purchase #3	$35.83	3.861%	$37.2134	$37.21	$37.20	$37.20
Purchase #4	$158.87	7.193%	$170.2975	$170.30	$170.30	$170.30
Purchase #5	$240.35	6.402%	$255.7372	$255.74	$255.75	$255.70
Purchase #6	$79.32	12.681%	$89.3786	$89.38	$89.40	$89.40
Purchase #7	$102.74	12.804%	$115.8948	$115.89	$115.90	$115.90
7 purchase totals =	$910.46		$979.1072	$979.11	$979.15	$979.10