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	$182.67	6.693%	$194.8961	$194.90	$194.90	$194.90
Purchase #2	$100.61	4.619%	$105.2572	$105.26	$105.25	$105.30
Purchase #3	$111.25	12.488%	$125.1429	$125.14	$125.15	$125.10
Purchase #4	$129.96	7.292%	$139.4367	$139.44	$139.45	$139.40
Purchase #5	$105.70	6.355%	$112.4172	$112.42	$112.40	$112.40
Purchase #6	$49.91	7.799%	$53.8025	$53.80	$53.80	$53.80
Purchase #7	$50.93	13.705%	$57.91	$57.91	$57.90	$57.90
7 purchase totals =	$731.03		$788.8626	$788.87	$788.85	$788.80