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	$178.85	7.265%	$191.8435	$191.84	$191.85	$191.80
Purchase #2	$235.25	4.274%	$245.3046	$245.30	$245.30	$245.30
Purchase #3	$27.73	11.864%	$31.0199	$31.02	$31.00	$31.00
Purchase #4	$53.44	11.236%	$59.4445	$59.44	$59.45	$59.40
Purchase #5	$235.61	11.251%	$262.1185	$262.12	$262.10	$262.10
Purchase #6	$212.33	12.222%	$238.281	$238.28	$238.30	$238.30
Purchase #7	$139.31	3.528%	$144.2249	$144.22	$144.20	$144.20
7 purchase totals =	$1,082.52		$1,172.2369	$1,172.22	$1,172.20	$1,172.10