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	$191.58	6.567%	$204.1611	$204.16	$204.15	$204.20
Purchase #2	$28.84	9.364%	$31.5406	$31.54	$31.55	$31.50
Purchase #3	$16.35	11.737%	$18.269	$18.27	$18.25	$18.30
Purchase #4	$119.61	10.271%	$131.8951	$131.90	$131.90	$131.90
Purchase #5	$86.38	5.820%	$91.4073	$91.41	$91.40	$91.40
Purchase #6	$77.25	11.467%	$86.1083	$86.11	$86.10	$86.10
Purchase #7	$239.85	5.506%	$253.0561	$253.06	$253.05	$253.10
7 purchase totals =	$759.86		$816.4375	$816.45	$816.40	$816.50