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	$61.74	11.340%	$68.7413	$68.74	$68.75	$68.70
Purchase #2	$18.40	8.712%	$20.003	$20.00	$20.00	$20.00
Purchase #3	$112.44	13.280%	$127.372	$127.37	$127.35	$127.40
Purchase #4	$82.31	3.832%	$85.4641	$85.46	$85.45	$85.50
Purchase #5	$241.98	9.563%	$265.1205	$265.12	$265.10	$265.10
Purchase #6	$147.91	13.375%	$167.693	$167.69	$167.70	$167.70
Purchase #7	$92.65	9.124%	$101.1034	$101.10	$101.10	$101.10
7 purchase totals =	$757.43		$835.4973	$835.48	$835.45	$835.50