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	$184.66	7.687%	$198.8548	$198.85	$198.85	$198.90
Purchase #2	$249.76	5.235%	$262.8349	$262.83	$262.85	$262.80
Purchase #3	$172.50	3.867%	$179.1706	$179.17	$179.15	$179.20
Purchase #4	$207.92	13.467%	$235.9206	$235.92	$235.90	$235.90
Purchase #5	$63.69	12.112%	$71.4041	$71.40	$71.40	$71.40
Purchase #6	$64.80	9.811%	$71.1575	$71.16	$71.15	$71.20
Purchase #7	$37.62	8.612%	$40.8598	$40.86	$40.85	$40.90
7 purchase totals =	$980.95		$1,060.2023	$1,060.19	$1,060.15	$1,060.30