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	$173.92	10.313%	$191.8564	$191.86	$191.85	$191.90
Purchase #2	$216.46	11.687%	$241.7577	$241.76	$241.75	$241.80
Purchase #3	$73.90	9.468%	$80.8969	$80.90	$80.90	$80.90
Purchase #4	$28.31	10.388%	$31.2508	$31.25	$31.25	$31.30
Purchase #5	$151.57	6.782%	$161.8495	$161.85	$161.85	$161.80
Purchase #6	$120.53	10.635%	$133.3484	$133.35	$133.35	$133.30
Purchase #7	$237.62	9.112%	$259.2719	$259.27	$259.25	$259.30
7 purchase totals =	$1,002.31		$1,100.2316	$1,100.24	$1,100.20	$1,100.30