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	$158.60	4.384%	$165.553	$165.55	$165.55	$165.60
Purchase #2	$147.78	13.160%	$167.2278	$167.23	$167.25	$167.20
Purchase #3	$53.79	10.300%	$59.3304	$59.33	$59.35	$59.30
Purchase #4	$25.43	11.677%	$28.3995	$28.40	$28.40	$28.40
Purchase #5	$194.56	6.202%	$206.6266	$206.63	$206.65	$206.60
Purchase #6	$183.97	13.637%	$209.058	$209.06	$209.05	$209.10
Purchase #7	$142.63	11.678%	$159.2863	$159.29	$159.30	$159.30
7 purchase totals =	$906.76		$995.4816	$995.49	$995.55	$995.50