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	$94.33	4.843%	$98.8984	$98.90	$98.90	$98.90
Purchase #2	$38.84	12.565%	$43.7202	$43.72	$43.70	$43.70
Purchase #3	$85.53	5.118%	$89.9074	$89.91	$89.90	$89.90
Purchase #4	$33.91	7.270%	$36.3753	$36.38	$36.40	$36.40
Purchase #5	$125.99	3.654%	$130.5937	$130.59	$130.60	$130.60
Purchase #6	$170.90	6.829%	$182.5708	$182.57	$182.55	$182.60
Purchase #7	$210.29	11.404%	$234.2715	$234.27	$234.25	$234.30
7 purchase totals =	$759.79		$816.3373	$816.34	$816.30	$816.40