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	$40.27	12.440%	$45.2796	$45.28	$45.30	$45.30
Purchase #2	$72.48	9.219%	$79.1619	$79.16	$79.15	$79.20
Purchase #3	$82.57	11.835%	$92.3422	$92.34	$92.35	$92.30
Purchase #4	$31.44	6.526%	$33.4918	$33.49	$33.50	$33.50
Purchase #5	$52.83	13.782%	$60.111	$60.11	$60.10	$60.10
Purchase #6	$72.79	9.347%	$79.5937	$79.59	$79.60	$79.60
Purchase #7	$9.73	3.412%	$10.062	$10.06	$10.05	$10.10
7 purchase totals =	$362.11		$400.0422	$400.03	$400.05	$400.10