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	$58.98	4.798%	$61.8099	$61.81	$61.80	$61.80
Purchase #2	$233.73	12.665%	$263.3319	$263.33	$263.35	$263.30
Purchase #3	$142.43	7.697%	$153.3928	$153.39	$153.40	$153.40
Purchase #4	$86.41	11.235%	$96.1182	$96.12	$96.10	$96.10
Purchase #5	$239.65	10.608%	$265.0721	$265.07	$265.05	$265.10
Purchase #6	$80.36	11.760%	$89.8103	$89.81	$89.80	$89.80
Purchase #7	$152.72	5.148%	$160.582	$160.58	$160.60	$160.60
7 purchase totals =	$994.28		$1,090.1172	$1,090.11	$1,090.10	$1,090.10