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	$98.39	11.334%	$109.5415	$109.54	$109.55	$109.50
Purchase #2	$138.50	12.493%	$155.8028	$155.80	$155.80	$155.80
Purchase #3	$148.64	4.764%	$155.7212	$155.72	$155.70	$155.70
Purchase #4	$64.72	10.566%	$71.5583	$71.56	$71.55	$71.60
Purchase #5	$200.55	5.401%	$211.3817	$211.38	$211.40	$211.40
Purchase #6	$156.65	9.445%	$171.4456	$171.45	$171.45	$171.40
Purchase #7	$185.88	5.459%	$196.0272	$196.03	$196.05	$196.00
7 purchase totals =	$993.33		$1,071.4783	$1,071.48	$1,071.50	$1,071.40