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	$83.61	5.398%	$88.1233	$88.12	$88.10	$88.10
Purchase #2	$206.96	6.450%	$220.3089	$220.31	$220.30	$220.30
Purchase #3	$205.96	7.312%	$221.0198	$221.02	$221.00	$221.00
Purchase #4	$196.92	9.568%	$215.7613	$215.76	$215.75	$215.80
Purchase #5	$159.56	13.658%	$181.3527	$181.35	$181.35	$181.40
Purchase #6	$67.80	5.271%	$71.3737	$71.37	$71.35	$71.40
Purchase #7	$69.55	12.794%	$78.4482	$78.45	$78.45	$78.40
7 purchase totals =	$990.36		$1,076.3879	$1,076.38	$1,076.30	$1,076.40