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	$175.25	7.231%	$187.9223	$187.92	$187.90	$187.90
Purchase #2	$92.51	9.628%	$101.4169	$101.42	$101.40	$101.40
Purchase #3	$47.65	11.507%	$53.1331	$53.13	$53.15	$53.10
Purchase #4	$118.35	6.359%	$125.8759	$125.88	$125.90	$125.90
Purchase #5	$89.89	3.404%	$92.9499	$92.95	$92.95	$92.90
Purchase #6	$49.70	7.608%	$53.4812	$53.48	$53.50	$53.50
Purchase #7	$51.40	12.111%	$57.6251	$57.63	$57.65	$57.60
7 purchase totals =	$624.75		$672.4044	$672.41	$672.45	$672.30