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	$175.73	5.284%	$185.0156	$185.02	$185.00	$185.00
Purchase #2	$125.43	4.360%	$130.8987	$130.90	$130.90	$130.90
Purchase #3	$205.41	5.360%	$216.42	$216.42	$216.40	$216.40
Purchase #4	$228.67	9.222%	$249.7579	$249.76	$249.75	$249.80
Purchase #5	$91.92	8.671%	$99.8904	$99.89	$99.90	$99.90
Purchase #6	$245.80	10.633%	$271.9359	$271.94	$271.95	$271.90
Purchase #7	$72.87	8.586%	$79.1266	$79.13	$79.15	$79.10
7 purchase totals =	$1,145.83		$1,233.0451	$1,233.06	$1,233.05	$1,233.00