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	$156.84	11.300%	$174.5629	$174.56	$174.55	$174.60
Purchase #2	$164.26	6.314%	$174.6314	$174.63	$174.65	$174.60
Purchase #3	$55.92	6.196%	$59.3848	$59.38	$59.40	$59.40
Purchase #4	$65.78	5.474%	$69.3808	$69.38	$69.40	$69.40
Purchase #5	$99.30	3.500%	$102.7755	$102.78	$102.80	$102.80
Purchase #6	$91.64	3.341%	$94.7017	$94.70	$94.70	$94.70
Purchase #7	$73.46	9.436%	$80.3917	$80.39	$80.40	$80.40
7 purchase totals =	$707.20		$755.8288	$755.82	$755.90	$755.90