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	$71.66	10.184%	$78.9579	$78.96	$78.95	$79.00
Purchase #2	$37.95	12.614%	$42.737	$42.74	$42.75	$42.70
Purchase #3	$168.60	7.395%	$181.068	$181.07	$181.05	$181.10
Purchase #4	$178.34	13.862%	$203.0615	$203.06	$203.05	$203.10
Purchase #5	$223.52	9.653%	$245.0964	$245.10	$245.10	$245.10
Purchase #6	$178.38	3.449%	$184.5323	$184.53	$184.55	$184.50
Purchase #7	$52.88	12.670%	$59.5799	$59.58	$59.60	$59.60
7 purchase totals =	$911.33		$995.0330	$995.04	$995.05	$995.10