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	$191.69	4.356%	$200.04	$200.04	$200.05	$200.00
Purchase #2	$65.45	10.834%	$72.5409	$72.54	$72.55	$72.50
Purchase #3	$54.73	11.623%	$61.0913	$61.09	$61.10	$61.10
Purchase #4	$157.82	10.384%	$174.208	$174.21	$174.20	$174.20
Purchase #5	$180.49	13.323%	$204.5367	$204.54	$204.55	$204.50
Purchase #6	$209.92	9.111%	$229.0458	$229.05	$229.05	$229.00
Purchase #7	$138.55	7.820%	$149.3846	$149.38	$149.40	$149.40
7 purchase totals =	$998.65		$1,090.8473	$1,090.85	$1,090.90	$1,090.70