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	$190.96	3.263%	$197.191	$197.19	$197.20	$197.20
Purchase #2	$39.63	5.526%	$41.82	$41.82	$41.80	$41.80
Purchase #3	$51.99	3.553%	$53.8372	$53.84	$53.85	$53.80
Purchase #4	$150.37	9.814%	$165.1273	$165.13	$165.15	$165.10
Purchase #5	$37.62	8.562%	$40.841	$40.84	$40.85	$40.80
Purchase #6	$183.56	8.348%	$198.8836	$198.88	$198.90	$198.90
Purchase #7	$92.46	8.330%	$100.1619	$100.16	$100.15	$100.20
7 purchase totals =	$746.59		$797.8620	$797.86	$797.90	$797.80