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	$180.54	12.453%	$203.0226	$203.02	$203.00	$203.00
Purchase #2	$139.88	8.819%	$152.216	$152.22	$152.20	$152.20
Purchase #3	$241.46	9.785%	$265.0869	$265.09	$265.10	$265.10
Purchase #4	$150.25	8.374%	$162.8319	$162.83	$162.85	$162.80
Purchase #5	$171.45	11.436%	$191.057	$191.06	$191.05	$191.10
Purchase #6	$42.58	6.241%	$45.2374	$45.24	$45.25	$45.20
Purchase #7	$53.42	4.663%	$55.911	$55.91	$55.90	$55.90
7 purchase totals =	$979.58		$1,075.3628	$1,075.37	$1,075.35	$1,075.30