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	$191.28	3.702%	$198.3612	$198.36	$198.35	$198.40
Purchase #2	$71.54	8.362%	$77.5222	$77.52	$77.50	$77.50
Purchase #3	$85.69	4.150%	$89.2461	$89.25	$89.25	$89.20
Purchase #4	$80.52	11.583%	$89.8466	$89.85	$89.85	$89.80
Purchase #5	$42.58	9.821%	$46.7618	$46.76	$46.75	$46.80
Purchase #6	$137.52	11.179%	$152.8934	$152.89	$152.90	$152.90
Purchase #7	$183.85	10.373%	$202.9208	$202.92	$202.90	$202.90
7 purchase totals =	$792.98		$857.5521	$857.55	$857.50	$857.50