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	$90.89	7.871%	$98.044	$98.04	$98.05	$98.00
Purchase #2	$191.56	12.706%	$215.8996	$215.90	$215.90	$215.90
Purchase #3	$240.46	4.287%	$250.7685	$250.77	$250.75	$250.80
Purchase #4	$7.84	5.600%	$8.279	$8.28	$8.30	$8.30
Purchase #5	$139.61	8.772%	$151.8566	$151.86	$151.85	$151.90
Purchase #6	$122.93	11.428%	$136.9784	$136.98	$137.00	$137.00
Purchase #7	$211.71	5.571%	$223.5044	$223.50	$223.50	$223.50
7 purchase totals =	$1,005.00		$1,085.3305	$1,085.33	$1,085.35	$1,085.40