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	$208.36	7.467%	$223.9182	$223.92	$223.90	$223.90
Purchase #2	$61.70	9.194%	$67.3727	$67.37	$67.35	$67.40
Purchase #3	$196.90	13.297%	$223.0818	$223.08	$223.10	$223.10
Purchase #4	$120.77	11.809%	$135.0317	$135.03	$135.05	$135.00
Purchase #5	$74.76	13.839%	$85.106	$85.11	$85.10	$85.10
Purchase #6	$72.90	7.165%	$78.1233	$78.12	$78.10	$78.10
Purchase #7	$164.77	12.744%	$185.7683	$185.77	$185.75	$185.80
7 purchase totals =	$900.16		$998.4020	$998.40	$998.35	$998.40