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	$83.41	9.330%	$91.1922	$91.19	$91.20	$91.20
Purchase #2	$93.34	6.695%	$99.5891	$99.59	$99.60	$99.60
Purchase #3	$184.91	6.292%	$196.5445	$196.54	$196.55	$196.50
Purchase #4	$207.45	11.664%	$231.647	$231.65	$231.65	$231.60
Purchase #5	$70.34	13.800%	$80.0469	$80.05	$80.05	$80.00
Purchase #6	$222.53	5.705%	$235.2253	$235.23	$235.25	$235.20
Purchase #7	$72.88	7.194%	$78.123	$78.12	$78.10	$78.10
7 purchase totals =	$934.86		$1,012.3680	$1,012.37	$1,012.40	$1,012.20