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	$159.36	8.543%	$172.9741	$172.97	$172.95	$173.00
Purchase #2	$75.57	8.700%	$82.1446	$82.14	$82.15	$82.10
Purchase #3	$33.63	11.253%	$37.4144	$37.41	$37.40	$37.40
Purchase #4	$170.52	4.463%	$178.1303	$178.13	$178.15	$178.10
Purchase #5	$73.43	6.449%	$78.1655	$78.17	$78.15	$78.20
Purchase #6	$204.41	5.348%	$215.3418	$215.34	$215.35	$215.30
Purchase #7	$43.33	5.414%	$45.6759	$45.68	$45.70	$45.70
7 purchase totals =	$760.25		$809.8466	$809.84	$809.85	$809.80