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	$73.99	8.242%	$80.0883	$80.09	$80.10	$80.10
Purchase #2	$154.40	13.498%	$175.2409	$175.24	$175.25	$175.20
Purchase #3	$126.29	11.113%	$140.3246	$140.32	$140.30	$140.30
Purchase #4	$170.87	11.455%	$190.4432	$190.44	$190.45	$190.40
Purchase #5	$42.46	7.198%	$45.5163	$45.52	$45.50	$45.50
Purchase #6	$214.54	8.792%	$233.4024	$233.40	$233.40	$233.40
Purchase #7	$153.53	4.148%	$159.8984	$159.90	$159.90	$159.90
7 purchase totals =	$936.08		$1,024.9141	$1,024.91	$1,024.90	$1,024.80