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	$154.54	11.467%	$172.2611	$172.26	$172.25	$172.30
Purchase #2	$135.74	6.507%	$144.5726	$144.57	$144.55	$144.60
Purchase #3	$203.54	12.283%	$228.5408	$228.54	$228.55	$228.50
Purchase #4	$194.37	11.849%	$217.4009	$217.40	$217.40	$217.40
Purchase #5	$37.95	6.269%	$40.3291	$40.33	$40.35	$40.30
Purchase #6	$249.67	5.596%	$263.6415	$263.64	$263.65	$263.60
Purchase #7	$72.78	13.677%	$82.7341	$82.73	$82.75	$82.70
7 purchase totals =	$1,048.59		$1,149.4801	$1,149.47	$1,149.50	$1,149.40