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	$167.28	8.404%	$181.3382	$181.34	$181.35	$181.30
Purchase #2	$44.73	3.128%	$46.1292	$46.13	$46.15	$46.10
Purchase #3	$90.27	11.597%	$100.7386	$100.74	$100.75	$100.70
Purchase #4	$89.29	6.228%	$94.851	$94.85	$94.85	$94.90
Purchase #5	$50.92	9.310%	$55.6607	$55.66	$55.65	$55.70
Purchase #6	$53.33	12.616%	$60.0581	$60.06	$60.05	$60.10
Purchase #7	$74.40	10.598%	$82.2849	$82.28	$82.30	$82.30
7 purchase totals =	$570.22		$621.0607	$621.06	$621.10	$621.10