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	$228.88	4.129%	$238.3305	$238.33	$238.35	$238.30
Purchase #2	$8.86	6.478%	$9.434	$9.43	$9.45	$9.40
Purchase #3	$58.66	5.498%	$61.8851	$61.89	$61.90	$61.90
Purchase #4	$207.96	7.160%	$222.8499	$222.85	$222.85	$222.80
Purchase #5	$248.73	12.345%	$279.4357	$279.44	$279.45	$279.40
Purchase #6	$149.53	8.731%	$162.5855	$162.59	$162.60	$162.60
Purchase #7	$181.35	13.420%	$205.6872	$205.69	$205.70	$205.70
7 purchase totals =	$1,083.97		$1,180.2079	$1,180.22	$1,180.30	$1,180.10