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	$157.34	10.285%	$173.5224	$173.52	$173.50	$173.50
Purchase #2	$69.41	4.793%	$72.7368	$72.74	$72.75	$72.70
Purchase #3	$172.86	12.471%	$194.4174	$194.42	$194.40	$194.40
Purchase #4	$123.41	5.604%	$130.3259	$130.33	$130.35	$130.30
Purchase #5	$205.74	13.584%	$233.6877	$233.69	$233.70	$233.70
Purchase #6	$48.51	10.755%	$53.7273	$53.73	$53.75	$53.70
Purchase #7	$157.43	9.221%	$171.9466	$171.95	$171.95	$171.90
7 purchase totals =	$934.70		$1,030.3641	$1,030.38	$1,030.40	$1,030.20