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	$138.53	10.260%	$152.7432	$152.74	$152.75	$152.70
Purchase #2	$49.88	12.261%	$55.9958	$56.00	$56.00	$56.00
Purchase #3	$55.40	6.572%	$59.0409	$59.04	$59.05	$59.00
Purchase #4	$82.31	10.451%	$90.9122	$90.91	$90.90	$90.90
Purchase #5	$28.88	11.490%	$32.1983	$32.20	$32.20	$32.20
Purchase #6	$73.62	4.112%	$76.6473	$76.65	$76.65	$76.60
Purchase #7	$205.89	13.418%	$233.5163	$233.52	$233.50	$233.50
7 purchase totals =	$634.51		$701.0540	$701.06	$701.05	$700.90