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	$76.32	5.159%	$80.2573	$80.26	$80.25	$80.30
Purchase #2	$130.48	11.290%	$145.2112	$145.21	$145.20	$145.20
Purchase #3	$29.65	12.396%	$33.3254	$33.33	$33.35	$33.30
Purchase #4	$144.46	12.309%	$162.2416	$162.24	$162.25	$162.20
Purchase #5	$162.32	13.559%	$184.329	$184.33	$184.35	$184.30
Purchase #6	$196.60	3.315%	$203.1173	$203.12	$203.10	$203.10
Purchase #7	$201.87	4.440%	$210.833	$210.83	$210.85	$210.80
7 purchase totals =	$941.70		$1,019.3148	$1,019.32	$1,019.35	$1,019.20