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	$222.92	8.799%	$242.5347	$242.53	$242.55	$242.50
Purchase #2	$142.88	10.267%	$157.5495	$157.55	$157.55	$157.50
Purchase #3	$106.49	4.818%	$111.6207	$111.62	$111.60	$111.60
Purchase #4	$96.79	3.260%	$99.9454	$99.95	$99.95	$99.90
Purchase #5	$195.28	10.165%	$215.1302	$215.13	$215.15	$215.10
Purchase #6	$248.66	8.314%	$269.3336	$269.33	$269.35	$269.30
Purchase #7	$217.89	6.146%	$231.2815	$231.28	$231.30	$231.30
7 purchase totals =	$1,230.91		$1,327.3956	$1,327.39	$1,327.45	$1,327.20