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	$141.50	4.504%	$147.8732	$147.87	$147.85	$147.90
Purchase #2	$73.94	5.406%	$77.9372	$77.94	$77.95	$77.90
Purchase #3	$192.96	13.534%	$219.0752	$219.08	$219.10	$219.10
Purchase #4	$78.89	8.597%	$85.6722	$85.67	$85.65	$85.70
Purchase #5	$131.47	8.324%	$142.4136	$142.41	$142.40	$142.40
Purchase #6	$152.65	8.834%	$166.1351	$166.14	$166.15	$166.10
Purchase #7	$167.33	8.172%	$181.0042	$181.00	$181.00	$181.00
7 purchase totals =	$938.74		$1,020.1107	$1,020.11	$1,020.10	$1,020.10