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	$133.35	10.867%	$147.8411	$147.84	$147.85	$147.80
Purchase #2	$119.33	3.755%	$123.8108	$123.81	$123.80	$123.80
Purchase #3	$190.36	3.265%	$196.5753	$196.58	$196.60	$196.60
Purchase #4	$200.62	11.139%	$222.9671	$222.97	$222.95	$223.00
Purchase #5	$196.29	11.346%	$218.5611	$218.56	$218.55	$218.60
Purchase #6	$76.69	10.112%	$84.4449	$84.44	$84.45	$84.40
Purchase #7	$55.63	3.212%	$57.4168	$57.42	$57.40	$57.40
7 purchase totals =	$972.27		$1,051.6171	$1,051.62	$1,051.60	$1,051.60