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	$87.80	10.140%	$96.7029	$96.70	$96.70	$96.70
Purchase #2	$17.32	12.377%	$19.4637	$19.46	$19.45	$19.50
Purchase #3	$96.45	10.413%	$106.4933	$106.49	$106.50	$106.50
Purchase #4	$58.50	6.834%	$62.4979	$62.50	$62.50	$62.50
Purchase #5	$50.76	6.212%	$53.9132	$53.91	$53.90	$53.90
Purchase #6	$161.42	6.241%	$171.4942	$171.49	$171.50	$171.50
Purchase #7	$112.28	13.406%	$127.3323	$127.33	$127.35	$127.30
7 purchase totals =	$584.53		$637.8975	$637.88	$637.90	$637.90