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	$116.44	6.707%	$124.2496	$124.25	$124.25	$124.20
Purchase #2	$146.56	3.822%	$152.1615	$152.16	$152.15	$152.20
Purchase #3	$76.28	7.652%	$82.1169	$82.12	$82.10	$82.10
Purchase #4	$242.50	5.515%	$255.8739	$255.87	$255.85	$255.90
Purchase #5	$248.27	8.156%	$268.5189	$268.52	$268.50	$268.50
Purchase #6	$232.51	7.302%	$249.4879	$249.49	$249.50	$249.50
Purchase #7	$54.86	9.639%	$60.148	$60.15	$60.15	$60.10
7 purchase totals =	$1,117.42		$1,192.5567	$1,192.56	$1,192.50	$1,192.50