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	$78.63	8.355%	$85.1995	$85.20	$85.20	$85.20
Purchase #2	$64.75	11.391%	$72.1257	$72.13	$72.15	$72.10
Purchase #3	$228.64	9.552%	$250.4797	$250.48	$250.50	$250.50
Purchase #4	$103.28	11.829%	$115.497	$115.50	$115.50	$115.50
Purchase #5	$179.78	6.452%	$191.3794	$191.38	$191.40	$191.40
Purchase #6	$188.96	6.257%	$200.7832	$200.78	$200.80	$200.80
Purchase #7	$145.26	10.421%	$160.3975	$160.40	$160.40	$160.40
7 purchase totals =	$989.30		$1,075.8620	$1,075.87	$1,075.95	$1,075.90