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	$243.73	13.513%	$276.6652	$276.67	$276.65	$276.70
Purchase #2	$223.33	6.780%	$238.4718	$238.47	$238.45	$238.50
Purchase #3	$64.78	10.543%	$71.6098	$71.61	$71.60	$71.60
Purchase #4	$188.60	11.587%	$210.4531	$210.45	$210.45	$210.50
Purchase #5	$158.72	9.621%	$173.9905	$173.99	$174.00	$174.00
Purchase #6	$218.93	9.429%	$239.5729	$239.57	$239.55	$239.60
Purchase #7	$188.28	4.261%	$196.3026	$196.30	$196.30	$196.30
7 purchase totals =	$1,286.37		$1,407.0659	$1,407.06	$1,407.00	$1,407.20