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	$53.79	10.140%	$59.2443	$59.24	$59.25	$59.20
Purchase #2	$158.82	7.402%	$170.5759	$170.58	$170.60	$170.60
Purchase #3	$31.77	11.427%	$35.4004	$35.40	$35.40	$35.40
Purchase #4	$221.92	3.171%	$228.9571	$228.96	$228.95	$229.00
Purchase #5	$237.54	13.460%	$269.5129	$269.51	$269.50	$269.50
Purchase #6	$94.99	4.231%	$99.009	$99.01	$99.00	$99.00
Purchase #7	$184.50	4.129%	$192.118	$192.12	$192.10	$192.10
7 purchase totals =	$983.33		$1,054.8176	$1,054.82	$1,054.80	$1,054.80