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	$174.36	7.429%	$187.3132	$187.31	$187.30	$187.30
Purchase #2	$88.63	3.742%	$91.9465	$91.95	$91.95	$91.90
Purchase #3	$196.42	13.231%	$222.4083	$222.41	$222.40	$222.40
Purchase #4	$188.52	6.122%	$200.0612	$200.06	$200.05	$200.10
Purchase #5	$142.59	9.550%	$156.2073	$156.21	$156.20	$156.20
Purchase #6	$142.90	6.740%	$152.5315	$152.53	$152.55	$152.50
Purchase #7	$127.41	7.538%	$137.0142	$137.01	$137.00	$137.00
7 purchase totals =	$1,060.83		$1,147.4822	$1,147.48	$1,147.45	$1,147.40