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	$52.48	13.104%	$59.357	$59.36	$59.35	$59.40
Purchase #2	$188.64	12.808%	$212.801	$212.80	$212.80	$212.80
Purchase #3	$118.83	7.322%	$127.5307	$127.53	$127.55	$127.50
Purchase #4	$197.93	5.838%	$209.4852	$209.49	$209.50	$209.50
Purchase #5	$101.51	12.415%	$114.1125	$114.11	$114.10	$114.10
Purchase #6	$238.82	9.174%	$260.7293	$260.73	$260.75	$260.70
Purchase #7	$30.25	7.200%	$32.428	$32.43	$32.45	$32.40
7 purchase totals =	$928.46		$1,016.4437	$1,016.45	$1,016.50	$1,016.40