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	$131.99	5.379%	$139.0897	$139.09	$139.10	$139.10
Purchase #2	$43.68	3.292%	$45.1179	$45.12	$45.10	$45.10
Purchase #3	$136.79	9.778%	$150.1653	$150.17	$150.15	$150.20
Purchase #4	$168.33	9.198%	$183.813	$183.81	$183.80	$183.80
Purchase #5	$149.88	8.651%	$162.8461	$162.85	$162.85	$162.80
Purchase #6	$229.86	11.275%	$255.7767	$255.78	$255.80	$255.80
Purchase #7	$110.98	11.839%	$124.1189	$124.12	$124.10	$124.10
7 purchase totals =	$971.51		$1,060.9276	$1,060.94	$1,060.90	$1,060.90