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	$173.59	6.376%	$184.6581	$184.66	$184.65	$184.70
Purchase #2	$219.27	8.744%	$238.443	$238.44	$238.45	$238.40
Purchase #3	$219.49	8.552%	$238.2608	$238.26	$238.25	$238.30
Purchase #4	$86.92	9.402%	$95.0922	$95.09	$95.10	$95.10
Purchase #5	$91.28	6.191%	$96.9311	$96.93	$96.95	$96.90
Purchase #6	$47.64	6.861%	$50.9086	$50.91	$50.90	$50.90
Purchase #7	$88.51	12.776%	$99.818	$99.82	$99.80	$99.80
7 purchase totals =	$926.70		$1,004.1118	$1,004.11	$1,004.10	$1,004.10