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	$56.76	9.527%	$62.1675	$62.17	$62.15	$62.20
Purchase #2	$89.56	11.192%	$99.5836	$99.58	$99.60	$99.60
Purchase #3	$157.89	9.134%	$172.3117	$172.31	$172.30	$172.30
Purchase #4	$130.50	9.471%	$142.8597	$142.86	$142.85	$142.90
Purchase #5	$79.44	7.392%	$85.3122	$85.31	$85.30	$85.30
Purchase #6	$27.46	9.756%	$30.139	$30.14	$30.15	$30.10
Purchase #7	$71.37	13.572%	$81.0563	$81.06	$81.05	$81.10
7 purchase totals =	$612.98		$673.4300	$673.43	$673.40	$673.50