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	$97.27	8.739%	$105.7704	$105.77	$105.75	$105.80
Purchase #2	$85.44	6.386%	$90.8962	$90.90	$90.90	$90.90
Purchase #3	$44.64	8.600%	$48.479	$48.48	$48.50	$48.50
Purchase #4	$228.97	8.529%	$248.4989	$248.50	$248.50	$248.50
Purchase #5	$202.48	9.355%	$221.422	$221.42	$221.40	$221.40
Purchase #6	$170.77	8.486%	$185.2615	$185.26	$185.25	$185.30
Purchase #7	$116.29	12.168%	$130.4402	$130.44	$130.45	$130.40
7 purchase totals =	$945.86		$1,030.7682	$1,030.77	$1,030.75	$1,030.80