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	$207.51	9.463%	$227.1467	$227.15	$227.15	$227.10
Purchase #2	$230.67	4.810%	$241.7652	$241.77	$241.75	$241.80
Purchase #3	$91.29	6.220%	$96.9682	$96.97	$96.95	$97.00
Purchase #4	$89.73	9.760%	$98.4876	$98.49	$98.50	$98.50
Purchase #5	$135.77	11.859%	$151.871	$151.87	$151.85	$151.90
Purchase #6	$185.30	3.526%	$191.8337	$191.83	$191.85	$191.80
Purchase #7	$35.61	9.204%	$38.8875	$38.89	$38.90	$38.90
7 purchase totals =	$975.88		$1,046.9599	$1,046.97	$1,046.95	$1,047.00