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	$93.44	9.243%	$102.0767	$102.08	$102.10	$102.10
Purchase #2	$139.83	5.799%	$147.9387	$147.94	$147.95	$147.90
Purchase #3	$153.79	9.415%	$168.2693	$168.27	$168.25	$168.30
Purchase #4	$80.83	10.415%	$89.2484	$89.25	$89.25	$89.20
Purchase #5	$78.96	4.860%	$82.7975	$82.80	$82.80	$82.80
Purchase #6	$96.76	13.720%	$110.0355	$110.04	$110.05	$110.00
Purchase #7	$87.98	4.670%	$92.0887	$92.09	$92.10	$92.10
7 purchase totals =	$731.59		$792.4548	$792.47	$792.50	$792.40