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	$174.93	12.410%	$196.6388	$196.64	$196.65	$196.60
Purchase #2	$130.32	12.629%	$146.7781	$146.78	$146.80	$146.80
Purchase #3	$131.98	7.607%	$142.0197	$142.02	$142.00	$142.00
Purchase #4	$152.73	12.436%	$171.7235	$171.72	$171.70	$171.70
Purchase #5	$185.76	6.356%	$197.5669	$197.57	$197.55	$197.60
Purchase #6	$93.41	6.744%	$99.7096	$99.71	$99.70	$99.70
Purchase #7	$98.30	6.516%	$104.7052	$104.71	$104.70	$104.70
7 purchase totals =	$967.43		$1,059.1418	$1,059.15	$1,059.10	$1,059.10