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	$88.89	10.618%	$98.3283	$98.33	$98.35	$98.30
Purchase #2	$97.80	13.591%	$111.092	$111.09	$111.10	$111.10
Purchase #3	$175.60	10.538%	$194.1047	$194.10	$194.10	$194.10
Purchase #4	$81.35	6.193%	$86.388	$86.39	$86.40	$86.40
Purchase #5	$210.79	6.131%	$223.7135	$223.71	$223.70	$223.70
Purchase #6	$216.58	12.108%	$242.8035	$242.80	$242.80	$242.80
Purchase #7	$50.76	6.839%	$54.2315	$54.23	$54.25	$54.20
7 purchase totals =	$921.77		$1,010.6615	$1,010.65	$1,010.70	$1,010.60