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	$213.31	6.459%	$227.0877	$227.09	$227.10	$227.10
Purchase #2	$244.41	4.707%	$255.9144	$255.91	$255.90	$255.90
Purchase #3	$60.85	7.275%	$65.2768	$65.28	$65.30	$65.30
Purchase #4	$110.56	3.482%	$114.4097	$114.41	$114.40	$114.40
Purchase #5	$74.27	5.754%	$78.5435	$78.54	$78.55	$78.50
Purchase #6	$167.95	4.331%	$175.2239	$175.22	$175.20	$175.20
Purchase #7	$53.81	4.585%	$56.2772	$56.28	$56.30	$56.30
7 purchase totals =	$925.16		$972.7332	$972.73	$972.75	$972.70