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	$165.81	5.557%	$175.0241	$175.02	$175.00	$175.00
Purchase #2	$148.75	3.518%	$153.983	$153.98	$154.00	$154.00
Purchase #3	$29.27	12.469%	$32.9197	$32.92	$32.90	$32.90
Purchase #4	$114.53	7.483%	$123.1003	$123.10	$123.10	$123.10
Purchase #5	$248.56	5.317%	$261.7759	$261.78	$261.80	$261.80
Purchase #6	$155.32	3.268%	$160.3959	$160.40	$160.40	$160.40
Purchase #7	$122.89	3.644%	$127.3681	$127.37	$127.35	$127.40
7 purchase totals =	$985.13		$1,034.5670	$1,034.57	$1,034.55	$1,034.60