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	$54.91	9.543%	$60.1501	$60.15	$60.15	$60.20
Purchase #2	$178.59	3.797%	$185.3711	$185.37	$185.35	$185.40
Purchase #3	$137.34	13.848%	$156.3588	$156.36	$156.35	$156.40
Purchase #4	$94.31	12.544%	$106.1402	$106.14	$106.15	$106.10
Purchase #5	$85.91	3.470%	$88.8911	$88.89	$88.90	$88.90
Purchase #6	$247.86	13.467%	$281.2393	$281.24	$281.25	$281.20
Purchase #7	$132.63	9.764%	$145.58	$145.58	$145.60	$145.60
7 purchase totals =	$931.55		$1,023.7306	$1,023.73	$1,023.75	$1,023.80