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	$92.28	7.352%	$99.0644	$99.06	$99.05	$99.10
Purchase #2	$168.73	11.334%	$187.8539	$187.85	$187.85	$187.90
Purchase #3	$46.82	7.613%	$50.3844	$50.38	$50.40	$50.40
Purchase #4	$61.84	9.658%	$67.8125	$67.81	$67.80	$67.80
Purchase #5	$181.53	5.152%	$190.8824	$190.88	$190.90	$190.90
Purchase #6	$53.80	6.373%	$57.2287	$57.23	$57.25	$57.20
Purchase #7	$72.90	10.503%	$80.5567	$80.56	$80.55	$80.60
7 purchase totals =	$677.90		$733.7830	$733.77	$733.80	$733.90