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	$124.37	13.346%	$140.9684	$140.97	$140.95	$141.00
Purchase #2	$85.61	5.251%	$90.1054	$90.11	$90.10	$90.10
Purchase #3	$143.75	4.855%	$150.7291	$150.73	$150.75	$150.70
Purchase #4	$219.59	11.648%	$245.1678	$245.17	$245.15	$245.20
Purchase #5	$139.85	8.773%	$152.119	$152.12	$152.10	$152.10
Purchase #6	$176.38	4.200%	$183.788	$183.79	$183.80	$183.80
Purchase #7	$83.99	5.422%	$88.5439	$88.54	$88.55	$88.50
7 purchase totals =	$973.54		$1,051.4216	$1,051.43	$1,051.40	$1,051.40