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	$98.30	11.696%	$109.7972	$109.80	$109.80	$109.80
Purchase #2	$158.75	7.800%	$171.1325	$171.13	$171.15	$171.10
Purchase #3	$94.72	5.350%	$99.7875	$99.79	$99.80	$99.80
Purchase #4	$190.37	10.690%	$210.7206	$210.72	$210.70	$210.70
Purchase #5	$246.93	7.519%	$265.4967	$265.50	$265.50	$265.50
Purchase #6	$138.31	10.507%	$152.8422	$152.84	$152.85	$152.80
Purchase #7	$147.40	9.160%	$160.9018	$160.90	$160.90	$160.90
7 purchase totals =	$1,074.78		$1,170.6785	$1,170.68	$1,170.70	$1,170.60