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	$205.37	11.144%	$228.2564	$228.26	$228.25	$228.30
Purchase #2	$223.33	10.856%	$247.5747	$247.57	$247.55	$247.60
Purchase #3	$111.36	12.169%	$124.9114	$124.91	$124.90	$124.90
Purchase #4	$74.92	4.717%	$78.454	$78.45	$78.45	$78.50
Purchase #5	$84.59	12.456%	$95.1265	$95.13	$95.15	$95.10
Purchase #6	$200.70	4.405%	$209.5408	$209.54	$209.55	$209.50
Purchase #7	$188.68	3.641%	$195.5498	$195.55	$195.55	$195.50
7 purchase totals =	$1,088.95		$1,179.4136	$1,179.41	$1,179.40	$1,179.40