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	$189.40	5.731%	$200.2545	$200.25	$200.25	$200.30
Purchase #2	$127.25	9.806%	$139.7281	$139.73	$139.75	$139.70
Purchase #3	$158.54	8.198%	$171.5371	$171.54	$171.55	$171.50
Purchase #4	$200.52	5.429%	$211.4062	$211.41	$211.40	$211.40
Purchase #5	$231.36	11.263%	$257.4181	$257.42	$257.40	$257.40
Purchase #6	$220.46	11.364%	$245.5131	$245.51	$245.50	$245.50
Purchase #7	$72.32	8.538%	$78.4947	$78.49	$78.50	$78.50
7 purchase totals =	$1,199.85		$1,304.3518	$1,304.35	$1,304.35	$1,304.30