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	$81.82	3.209%	$84.4456	$84.45	$84.45	$84.40
Purchase #2	$218.34	12.578%	$245.8028	$245.80	$245.80	$245.80
Purchase #3	$39.33	6.440%	$41.8629	$41.86	$41.85	$41.90
Purchase #4	$69.49	3.503%	$71.9242	$71.92	$71.90	$71.90
Purchase #5	$222.86	9.206%	$243.3765	$243.38	$243.40	$243.40
Purchase #6	$202.52	10.519%	$223.8231	$223.82	$223.80	$223.80
Purchase #7	$150.70	3.600%	$156.1252	$156.13	$156.15	$156.10
7 purchase totals =	$985.06		$1,067.3603	$1,067.36	$1,067.35	$1,067.30