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	$77.33	12.324%	$86.8601	$86.86	$86.85	$86.90
Purchase #2	$31.34	12.362%	$35.2143	$35.21	$35.20	$35.20
Purchase #3	$184.94	3.672%	$191.731	$191.73	$191.75	$191.70
Purchase #4	$36.27	13.547%	$41.1835	$41.18	$41.20	$41.20
Purchase #5	$42.36	11.599%	$47.2733	$47.27	$47.25	$47.30
Purchase #6	$110.72	3.537%	$114.6362	$114.64	$114.65	$114.60
Purchase #7	$37.81	4.270%	$39.4245	$39.42	$39.40	$39.40
7 purchase totals =	$520.77		$556.3229	$556.31	$556.30	$556.30