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	$195.54	11.498%	$218.0232	$218.02	$218.00	$218.00
Purchase #2	$141.69	5.687%	$149.7479	$149.75	$149.75	$149.70
Purchase #3	$91.40	9.690%	$100.2567	$100.26	$100.25	$100.30
Purchase #4	$38.90	4.109%	$40.4984	$40.50	$40.50	$40.50
Purchase #5	$83.31	13.224%	$94.3269	$94.33	$94.35	$94.30
Purchase #6	$165.81	3.335%	$171.3398	$171.34	$171.35	$171.30
Purchase #7	$190.30	10.119%	$209.5565	$209.56	$209.55	$209.60
7 purchase totals =	$906.95		$983.7494	$983.76	$983.75	$983.70