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	$50.51	6.561%	$53.824	$53.82	$53.80	$53.80
Purchase #2	$39.40	7.138%	$42.2124	$42.21	$42.20	$42.20
Purchase #3	$209.75	11.145%	$233.1266	$233.13	$233.15	$233.10
Purchase #4	$9.94	3.695%	$10.3073	$10.31	$10.30	$10.30
Purchase #5	$105.52	4.402%	$110.165	$110.17	$110.15	$110.20
Purchase #6	$38.28	3.518%	$39.6267	$39.63	$39.65	$39.60
Purchase #7	$182.30	6.718%	$194.5469	$194.55	$194.55	$194.50
7 purchase totals =	$635.70		$683.8089	$683.82	$683.80	$683.70