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	$60.71	10.556%	$67.1185	$67.12	$67.10	$67.10
Purchase #2	$199.93	5.202%	$210.3304	$210.33	$210.35	$210.30
Purchase #3	$88.72	12.608%	$99.9058	$99.91	$99.90	$99.90
Purchase #4	$139.82	9.323%	$152.8554	$152.86	$152.85	$152.90
Purchase #5	$48.96	3.419%	$50.6339	$50.63	$50.65	$50.60
Purchase #6	$170.56	9.746%	$187.1828	$187.18	$187.20	$187.20
Purchase #7	$233.82	8.233%	$253.0704	$253.07	$253.05	$253.10
7 purchase totals =	$942.52		$1,021.0972	$1,021.10	$1,021.10	$1,021.10