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	$89.33	12.657%	$100.6365	$100.64	$100.65	$100.60
Purchase #2	$194.70	6.865%	$208.0662	$208.07	$208.05	$208.10
Purchase #3	$229.73	3.320%	$237.357	$237.36	$237.35	$237.40
Purchase #4	$200.35	11.526%	$223.4423	$223.44	$223.45	$223.40
Purchase #5	$11.98	12.203%	$13.4419	$13.44	$13.45	$13.40
Purchase #6	$193.40	6.148%	$205.2902	$205.29	$205.30	$205.30
Purchase #7	$58.57	7.104%	$62.7308	$62.73	$62.75	$62.70
7 purchase totals =	$978.06		$1,050.9649	$1,050.97	$1,051.00	$1,050.90