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	$89.56	10.317%	$98.7999	$98.80	$98.80	$98.80
Purchase #2	$107.31	7.489%	$115.3464	$115.35	$115.35	$115.30
Purchase #3	$165.40	9.567%	$181.2238	$181.22	$181.20	$181.20
Purchase #4	$107.30	3.536%	$111.0941	$111.09	$111.10	$111.10
Purchase #5	$56.38	6.281%	$59.9212	$59.92	$59.90	$59.90
Purchase #6	$99.61	6.715%	$106.2988	$106.30	$106.30	$106.30
Purchase #7	$236.36	11.819%	$264.2954	$264.30	$264.30	$264.30
7 purchase totals =	$861.92		$936.9796	$936.98	$936.95	$936.90