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	$196.85	6.823%	$210.2811	$210.28	$210.30	$210.30
Purchase #2	$69.35	8.237%	$75.0624	$75.06	$75.05	$75.10
Purchase #3	$53.87	10.633%	$59.598	$59.60	$59.60	$59.60
Purchase #4	$96.89	3.689%	$100.4643	$100.46	$100.45	$100.50
Purchase #5	$39.78	9.653%	$43.62	$43.62	$43.60	$43.60
Purchase #6	$111.36	8.383%	$120.6953	$120.70	$120.70	$120.70
Purchase #7	$191.33	9.289%	$209.1026	$209.10	$209.10	$209.10
7 purchase totals =	$759.43		$818.8237	$818.82	$818.80	$818.90