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	$171.89	6.133%	$182.432	$182.43	$182.45	$182.40
Purchase #2	$240.69	9.692%	$264.0177	$264.02	$264.00	$264.00
Purchase #3	$152.47	8.772%	$165.8447	$165.84	$165.85	$165.80
Purchase #4	$209.28	11.501%	$233.3493	$233.35	$233.35	$233.30
Purchase #5	$88.99	8.351%	$96.4216	$96.42	$96.40	$96.40
Purchase #6	$65.59	6.546%	$69.8835	$69.88	$69.90	$69.90
Purchase #7	$66.42	10.376%	$73.3117	$73.31	$73.30	$73.30
7 purchase totals =	$995.33		$1,085.2605	$1,085.25	$1,085.25	$1,085.10