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	$174.46	9.837%	$191.6216	$191.62	$191.60	$191.60
Purchase #2	$215.37	6.663%	$229.7201	$229.72	$229.70	$229.70
Purchase #3	$97.48	4.801%	$102.16	$102.16	$102.15	$102.20
Purchase #4	$14.64	6.558%	$15.6001	$15.60	$15.60	$15.60
Purchase #5	$41.39	3.511%	$42.8432	$42.84	$42.85	$42.80
Purchase #6	$138.39	6.647%	$147.5888	$147.59	$147.60	$147.60
Purchase #7	$61.62	4.549%	$64.4231	$64.42	$64.40	$64.40
7 purchase totals =	$743.35		$793.9569	$793.95	$793.90	$793.90